Recyclable barrier paper

ABSTRACT

A barrier paper having a paper substrate having a front side and a back side opposite the front side, and a barrier layer disposed to the front side of the paper substrate. The barrier layer has of a polymeric binder and a wax based on a vegetable oil, the use of a barrier paper as wrapping paper, lining paper, paper for inner-bag packaging, interleaving paper and/or release paper for foods, and also to a method for producing a barrier paper.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a U.S. national stage of Application No. PCT/EP2018/085566 filedDec. 18, 2018. Priority is claimed on German Application No. DE 10 2017131 277.3 filed Dec. 22, 2017 the content of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a barrier paper, to the use of abarrier paper of the invention as wrapping paper, lining paper, paperfor inner-bag packaging, interleaving paper and/or release paper forfoods, and a method for producing a barrier paper.

2. Description of Related Art

Customers of foods that are sold loose, such as sausage, cheese, orbakery products, typically receive their products, for reasons ofhygiene or freshness retention, in packaging. Stringent requirementswith regard to packaging are imposed in particular in the case of fattyfoods. Where conventional, paper-based packaging is used, the packagingmaterial in the case of fatty foods may be penetrated by the fat fromthe food. This may result in the packaging material softening andtearing, or in the fat contaminating other articles if they come intocontact with the packaging.

WO 2007/050964 A1 describes a fat-resistant and water-resistant articlethat comprises a coating of a paraffin wax and polyvinyl alcohol.

US 2003/0152707 A1 describes a carrier coated with a wax made from avegetable oil, and which is highly resistant to water.

DE 10 2014 119 572 A1 describes a packaging paper for foods that has anareal density of between 20 g/m² and 40 g/m² and that has a massfraction of filler of less than 20%, based on the mass of the uncoatedpaper. The packaging paper at least on one side has a coating thatcomprises a polymer-encapsulated vegetable oil, talc, and a binder.

Fatty foods are frequently packaged using a wood-free, fatproof“greaseproof” paper, which by virtue of wet beating of the fibrousmaterials, has a certain fat resistance. Frequently, however, the fatresistance of these greaseproof papers is inadequate.

Wet beating is achieved by wide bars set widely apart or by basalt rockbarring in conjunction with a long beating time. The fibers, rather thanbeing shredded, are squeezed. This produces a high swelling fibermucilage, a slimy and greasy pulp, which undergoes only slow dewateringon the paper machine. The paper acquires a high density, but losesopacity. It becomes glassily translucent. Where the extent of fibershortening is low, the term “long wet” is used. Fibers shortened to agreater extent are referred to as “short wet”. Where the substrate ismade predominantly short wet fibers, its tear initiation resistance andtearing resistance are only low.

Frequently used as a more fat-resistant alternative to greaseproof paperis composite packaging. Composite packaging may consist, for example, ofa composite formed from a paper and from a polymeric and/or aluminumfoil. If no polyethylene coating (PE) takes place, fluorocarbons can beused as water-repellent chemicals. Paper here is coated for example onone side with polyethylene, frequently in an extrusion process, or withan aluminum foil. Composite packaging of this kind is notable for highfat resistance. This composite packaging, however, cannot easily bepassed for paper recycling, since first it is necessary for the foillayer to be removed. Nor is it possible to compost these composites,because the polymeric or aluminum foils used do not biodegrade.

Moreover, the growing concern about the scarcity of fossil, nonrenewableresources, such as petroleum or natural gas, has resulted in a steadilygrowing interest in the production of materials from renewable rawmaterials. Reference may be made in this context to, for example,polyethylene furanoate, a plastic based on 2,5-furandicarboxylic acid,the starting substances of which may be produced from sugars. It hasemerged, however, that the existing polymers produced from renewable rawmaterials either are nonbiodegradable or do not have the propertiesneeded for use in packaging materials.

The requirements imposed on the barrier paper, namely a high and/ordefined resistance to penetration by fats, oils, water, and water vapor,and high reusability or biodegradability, are requirements thattypically contradict one another. Within industry, therefore, there is agreat demand to provide packaging paper for food that can be producedwholly or predominantly from renewable raw materials and at the sametime can be effectively reused or biodegraded.

SUMMARY OF THE INVENTION

It is an object of one aspect of the present invention to provide abarrier paper for food contact that exhibits high resistance to fats,and/or oils, and/or moisture, and/or water or water vapor, and at thesame time can be produced wholly or predominantly from renewable rawmaterials. Additionally it is desirable if the barrier paper can bereadily reused or biodegraded, i.e., composted.

One aspect of the invention is a barrier paper 10 comprising:

-   -   a) a paper substrate 11 having a front side and a back side        opposite the front side,

and

-   -   b) a barrier layer 12 disposed to the front side and/or the back        side of the paper substrate,

wherein the barrier layer 12 comprises or consists of a polymeric binderand a wax based on a vegetable oil.

Surprisingly it has emerged that barrier papers according to one aspectof the invention exhibit high resistance to fats and/or oils and/ormoisture and at the same time can be produced wholly or predominantlyfrom renewable raw materials. As a result of the use of a polymericbinder, surprisingly, the barrier layer is designed such that it doesnot part from the paper substrate or that the wax transfers to otherarticles or the foods.

In the context of one aspect of the invention, a wax based on avegetable oil is understood to mean a wax obtained by chemicalmodification of a vegetable oil. The chemical modification may, forexample, be a partial or complete hydrogenation with a metalliccatalyst, for example nickel, and hydrogen, wherein all or some of thedouble bonds in the oil are hydrogenated to single bonds. Unlikevegetable oils, waxes are not in liquid form but in solid form at 20° C.The effect of the chemical modification of the vegetable oil is thus anincrease in the melting point.

A vegetable oil is understood to mean a fatty acid triglyceride that isobtained from plants or plant parts. The oil is typically obtained bypressing, extraction or refining of the oils from the plants or plantparts. The obtaining of the oils is known to the person skilled in theart. If plant seeds are used for obtaining oil, these are referred to asoilseeds. The oil in the seeds is in the form of lipids that constitutethe cell membranes and energy reserves thereof. Depending on theproportion of unsaturated fatty acids in the oil, a distinction is madebetween nondrying oils (for example olive oil), semidrying oils (forexample soybean oil or rapeseed oil) and drying oils (for examplelinseed oil or poppyseed oil). The term “drying” here does not meanevaporation, but rather the solidification of the oil caused byoxidation and polymerization of the unsaturated fatty acids. Preferenceis given to the use of semidrying and drying oils as starting materialfor production of the waxes used in accordance with one aspect of theinvention.

Possible sources for vegetable oil are açaí oil, algae oil, argan oil(from the fruit of the argan tree), avocado oil (from the fruit flesh ofthe avocado from the avocado tree), babaçu oil, cottonseed oil (from theseeds of the cotton plant), borage oil or borageseed oil (from the seedsof the borage plant), cupuaçu butter, cashewshell oil, safflower oil(also called “saflor oil”, from the seeds of the safflower orcarthamus), peanut oil (from the fruit of the peanut plant), hazelnutoil (from hazelnuts from the hazelnut bush), hemp oil (from the seeds ofedible hemp), Jatropha oil (from the seeds of Jatropha curcas), jojobaoil (actually a liquid wax; from the seeds of the jojoba bush), Camelliaoil (from the seeds of Camellia oleifera, Camellia sinensis or Camelliajaponica), cocoa butter, coconut oil (from the seed flesh of thecoconut, the tree fruit of the coconut palm), pumpkinseed oil (alsoreferred to as seed oil; from the seed kernels of the Styrian oilpumpkin), linseed oil (from ripe linseeds from flax), false flax oil(from the seeds of the false flax, Brassicaceae family), macadamia oil(from the nuts of the macadamia tree), maize kernel oil (from thekernels of maize), almond oil (from almonds from the almond tree), mangobutter (from Mangifera indica), apricot kernel oil (from the apricotkernel—i.e., the almond of the apricot stone—the apricot), poppyseed oil(from the seed grains of the poppy), evening primrose oil, olive oil(from the fruit flesh and core of the olive, the fruit of the olivetree), palm oil (from the fruit flesh of the palm fruit, the fruit ofthe oil palm), palm kernel oil (from the kernels of the palm fruit, thefruit of the oil palm), papaya oil, pistachio oil, pecan nut oil,perilla oil from the seeds of the perilla plant (shiso, sesame leaf),rapeseed oil (from the seeds of rape, Brassicaceae family), rice oil,castor oil (from the seeds of the castor oil plant), sea buckthorn oil(from the fruit flesh of the sea buckthorn berry, the fruit of the seabuckthorn bush), sea buckthorn kernel oil (from the kernels of the seabuckthorn berry, the fruit of the sea buckthorn bush), mustard oil (fromthe seed kernels of black mustard), black cumin oil (from the seeds ofthe fruit capsule of the black cumin plant), sesame oil (from the seedsof the sesame plant), shea butter (from the seeds of the shea nut tree),soya oil (from the beans of the soybean), sunflower oil (from thekernels of the sunflower), tung oil, walnut oil (from the kernels of thenuts from the walnut tree), watermelonseed oil, grapeseed oil (from thekernels of the fruits (grapes) of the grape plant or grapevine), wheatgerm oil (from the germ of wheat) and/or cedar oil (from the wood of theLebanon cedar), and the like. This list should not be regarded asconclusive; it shows ways of obtaining vegetable oils that can beconverted to a wax used in accordance with the invention.

Preference is given in accordance with one aspect of the invention to abarrier paper wherein the wax based on a vegetable oil is a wax based onan oil selected from the list encompassing palm oil, coconut oil,poppyseed oil, olive oil, linseed oil, soybean oil, sunflower oil,safflower oil, and rapeseed oil, the wax based on a vegetable oilpreferably being a wax based on a soybean oil, i.e., soybean oil wax orsoy wax.

Our own investigations have shown that waxes made from the oilsspecified as preferred above have particularly good properties. Thewaxes produced from these oils are notable for high durability and canbe produced with high melting points. The waxes used in accordance withone aspect of the invention, namely palm oil wax, coconut oil wax,poppyseed oil wax, olive oil wax, linseed oil wax, soybean oil wax,sunflower oil wax, safflower oil wax, and rapeseed oil wax, show asignificant increase in resistance to fats and/or oils and/or moisturewhen used in barrier papers of the invention. In particular, the use ofsoybean oil wax is preferred in accordance with the invention. Our owninvestigations have shown that, when soybean oil wax is used, not onlythe resistance to fat, oil, and moisture but also very low water vaporpermeability can be obtained. Soybean oil wax additionally has theadvantage that it can be produced in taste- and odor-neutral form.

Preference is given in accordance with the invention to barrier paperswherein the wax has a melting point above 40° C., preferably above 50°C., more preferably above 60° C.

Our own investigations have shown that it is already possible to achievevery good results when waxes having a melting point above 20° C. areused. However, it has been found that, surprisingly, when waxes having amelting point above 40° C. are used, the resistance of the barrierpapers to mechanical stress can be enhanced. This resistance is enhancedeven further at even higher melting points of the waxes. Our owninvestigations have additionally shown that the optimal melting point ofthe waxes is in the range from 60 to 80° C. if the barrier papers are tobe used at temperatures between 6° C. and 30° C. If the barrier papersare also to be employed at higher temperatures, it may be advisable touse a wax having a higher melting point.

Preference is given in accordance with one aspect of the invention tobarrier papers wherein the mass fraction of the wax based on a vegetableoil in the barrier layer is 6 to 98%, preferably 20 to 90%, morepreferably 50 to 89%, very preferably 50 to 78%, based on the total massof the barrier layer.

Our own investigations have shown that, surprisingly, there is adisproportionately significant decrease in fat, oil, and moisturebarrier properties in the case of a mass fraction of the wax based on avegetable oil below 6%, whereas excellent barrier properties can beobtained in the case of a mass fraction of the wax based on a vegetableoil above 98%, but there is a disproportionately significant decrease inthe mechanical stability of the barrier layer. Our own investigationshave shown that particularly good barrier papers with optimal barrierand mechanical properties can be obtained when the mass fraction of thewax based on a vegetable oil is 50 to 89%, preferably 50 to 78%.

Suitable polymeric binders are all binders that are customary inpapermaking. Our own investigations, however, have shown that a suitableselection of the binder may significantly improve the mechanicalproperties of the barrier layer and/or the biodegradability of thebarrier paper. Our own investigations have shown that it is advantageousand therefore preferred in accordance with the invention if thepolymeric binder is a crosslinked or noncrosslinked binder selected fromthe group consisting of starch, polyvinyl alcohol, carboxylgroup-modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer, acombination of polyvinyl alcohol and ethylene-vinyl alcohol copolymer,ethylene-vinyl acetate copolymer, silanol group-modified polyvinylalcohol, diacetone-modified polyvinyl alcohol, modified polyethyleneglycol, unmodified polyethylene glycol,α-isodecyl-ω-hydroxy-poly(oxy-1,2-ethanediyl), styrene-butadiene latex,styrene-acrylate polymers, acrylic copolymers, and mixtures thereof.

Our own investigations have revealed that barrier papers of one aspectof the invention have particularly high resistance to fat, oil, andmoisture if the polymeric binder is one or more styrene-acrylatepolymers or the binder comprises the latter.

Of the binders stated above, ethylene-vinyl alcohol copolymer andpolyvinyl alcohol are the least preferred. Particular preference istherefore given to barrier papers of one aspect of the invention, whichdo not comprise ethylene-vinyl alcohol copolymer and/or polyvinylalcohol in the barrier layer.

It is preferred in accordance with one aspect of the invention if thebarrier layer comprises no ethylene.

It is preferred here in accordance with one aspect of the invention hereif the mass fraction of the polymeric binder in the barrier layer is 94to 2%, preferably 80 to 10%, more preferably 50 to 11%, based on thetotal mass of the barrier layer.

Our own investigations have shown that an amount of polymeric bindersbelow a mass fraction of 2% leads to barrier papers wherein there is adisproportionately significant decrease in the mechanical resistance ofthe barrier layer. Where an amount of polymeric binders is above a massfraction of 94%, the mechanical resistance of the barrier layer isindeed sufficiently high, although it has emerged that there is adisproportionately significant decrease in the barrier properties withrespect to fat, oil, and moisture. Our own investigations here haverevealed that particularly good barrier papers having optimum barrierproperties and mechanical properties can be obtained if the amount ofpolymeric binders amounts to a mass fraction 50 to 11%.

It is particularly preferred here in accordance with one aspect of theinvention if the mass fraction of the polymeric binder in the barrierlayer is 94 to 2% and the mass fraction of the wax in the barrier layeris 6 to 98%, and it is further preferred if the mass fraction of thepolymeric binder in the barrier layer is 80 to 10% and the mass fractionof the wax in the barrier layer is 80 to 90%, and it is preferred stillfurther if the mass fraction of the polymeric binder in the barrierlayer is 50 to 11% and the mass fraction of the wax in the barrier layeris 50 to 89%.

Preferred in accordance with one aspect of the invention are barrierpapers wherein the mass per unit area of the barrier layer is in therange from 1.5 to 8 g/m², preferably in the range from 2.0 to 5.5 g/m²,more preferably in the range from 3.0 to 5.0 g/m². It has surprisinglyemerged that barrier papers with the low masses per unit area asspecified here have very good resistances with respect to fat, oil, andmoisture. While the resistance can be slightly improved by increasingthe mass per unit area, the improvement is only minimal, and so theslight improvement is not justified by increased consumption ofmaterial. At a mass per unit area of below 1.5 g/m², the resistance ofthe pure carrier substrate is indeed likewise improved, but theresistance is not always sufficient for certain areas of application(e.g., very fatty and moist foods). Our own investigations have shownthat an optimum resistance can be obtained if the mass per unit area ofthe barrier layer is in the range from 3.0 to 5.0 g/m².

Our own investigations have shown that it is particularly advantageousif the polymeric binder consists of two or more binders and at least onebinder is an anionic binder. An anionic binder here is understood tomean a binder that comprises a plurality of negative charges, which arestabilized by cations (e.g., metal cations or ammonium).

In the context of the present invention, a polymeric binder isunderstood to mean a binder which has been synthesized bypolycondensation from a multitude of molecules, and in which one or morekinds of atoms or atomic moieties (called repeat units) are strungtogether repeatedly, with the number of repeat units per molecule beingmore than 25.

It is preferred here in accordance with one aspect of the invention ifthe glass transition temperature of the anionic binder as determined bydifferential scanning calorimetry (DSC) is less than or equal to 120° C.Our own investigations have shown that at a glass transition temperatureof above 120° C., it is very difficult to produce the barrier layer, andthe barrier papers that are produced do not have such good properties asbarrier papers of the invention that have been produced using an anionicbinder having a glass transition temperature of less than or equal to120° C.

It is preferred in accordance with one aspect of the invention here ifthe anionic binder is a copolymer.

Suitable anionic binders are, for example, partly or fully deprotonatedpolyacrylic acid (or copolymers thereof, with acrylic esters, forexample), partly or fully deprotonated polymethacrylic acid (orcopolymers thereof, with methacrylic esters, for example), copolymers ofpolyacrylic esters (preferably methyl or ethyl esters), copolymers ofpolymethacrylic esters (preferably methyl or ethyl esters), orpolyacrylamides, or copolymers thereof.

It is preferred in accordance with one aspect of the invention if anaqueous solution or dispersion of the anionic binder has a basic pH,where present in dispersion or solution in water with a mass fraction of10%, and preferably in the range from 8 to 10.

To determine the pH of the anionic binder, an aqueous solution ordispersion of the anionic binder can be prepared that has a massfraction of 10%, and the pH can be determine by customary means.

In a likewise preferred aspect of the present invention, the barrierlayer (12) additionally comprises a wax based on saturated hydrocarbons.

Our own investigations have surprisingly shown that the combination of awax based on a vegetable oil and a wax based on saturated hydrocarbonsleads to particularly good resistance toward fats and/or oils and/ormoisture and/or water or water vapor. The combination of saturatedhydrocarbons and fatty acid triglyceride waxes appears to lead to layershaving particularly high molecular densities. Without wishing to be tiedto any particular theory, the high molecular density may be explained bythe saturated hydrocarbons filling up the lipophilic parts of the fattyacid triglyceride waxes. As a result, a resistance is achieved whichcannot be achieved only with the fatty acid triglyceride waxes or withwaxes based on saturated hydrocarbons. The combination of a wax based ona vegetable oil and a wax based on saturated hydrocarbons thereforeexhibits a synergistic effect, resulting in particularly good resistancewith respect to fats and/or oils and/or moisture and/or water or watervapor.

This synergistic effect is particularly pronounced if the wax based onsaturated hydrocarbons is octacosane and/or the wax based on a vegetableoil is a wax based on soybean oil.

Preference is given in accordance with the invention to barrier paperswherein the wax based on saturated hydrocarbons has a melting pointabove 40° C., preferably above 50° C., more preferably above 60° C.

Preference is given in accordance with the invention to barrier paperswherein the wax based on saturated hydrocarbons comprises or consists ofone, two, three or more than three alkanes selected from the groupconsisting of heneicosane, docosane, tricosane, tetracosane,pentacosane, hexacosane, heptacosane, octacosane, nonacosane,triacontane, hentriacontane, dotriacontane, tritriacontane,tetratriacontane, pentatriacontane, hexatriacontane, heptatriacontane,octatriacontane, and nonatriacontane, preferably selected from the groupconsisting of hexacosane, heptacosane, octacosane, nonacosane, andtriacontane. Particular preference is given in accordance with theinvention to barrier papers wherein the wax based on saturatedhydrocarbons is a wax based on octacosane.

More preferably in accordance with the invention, the acrylate copolymerin the barrier layer is a copolymer having an average molar mass in therange from 50000 to 150000 g/mol, preferably in the range from 80000 to130000 g/mol, more preferably in the range from 90000 to 100000 g/mol.The average molar mass is determined here with the aid of gel permeationchromatography (GPC) with tetrahydrofuran (THF; tetramethylene oxide;1,4-epoxybutane; oxacyclopentane) as solvent, polystyrene as standard,and detection by RI detector (refractive index detector).

More preferably in accordance with the invention, the acrylate copolymerin the barrier layer is a copolymer prepared using two, three, four,five, six or all monomers selected from the group consisting of methylacrylate, methyl methacrylate, butyl acrylate, butyl methacrylate,2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, and styrene.

Through a selection of the monomers used for preparation of the acrylatecopolymer, it is possible to optimize the properties of the resultingacrylate copolymer. Our own investigations have surprisingly shown herethat an acrylate copolymer that has been prepared from methyl acrylate,methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexylacrylate, 2-ethylhexyl methacrylate and/or styrene has particularly goodbarrier properties.

As well as methyl acrylate, methyl methacrylate, butyl acrylate, butylmethacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, andstyrene, further monomers may have been used here for preparation of theacrylate copolymer, or the copolymer has been prepared from two, three,four, five, six or all monomers selected from the group consisting ofmethyl acrylate, methyl methacrylate, butyl acrylate, butylmethacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, andstyrene.

More preferably in accordance with one aspect of the invention, theacrylate copolymer is a random copolymer.

Particularly preferred in accordance with one aspect of the invention isa barrier paper (10) comprising

-   -   a) a paper substrate 11 comprising a front side and a back side        opposite the front side,

and

-   -   b) a barrier layer 12 disposed to the front side and/or back        side of the paper substrate and consisting of or comprising        -   i) an acrylate copolymer having an average molar mass in the            range from 50000 to 150000 g/mol, the acrylate copolymer            having been prepared from two, three, four, five, six or            seven monomers selected from the group consisting of methyl            acrylate, methyl methacrylate, butyl acrylate, butyl            methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl            methacrylate, and styrene,        -   and        -   ii) a wax based on saturated hydrocarbons, the wax based on            saturated hydrocarbons preferably being octacosane or the            wax based on saturated hydrocarbons preferably comprising            octacosane,        -   and        -   iii) a wax based on a vegetable oil.

Preference is given in accordance with the invention to a barrier paperwherein the mass ratio between the polymeric binder and the wax based onsaturated hydrocarbons is 999:1 to 70:30, preferably 99:1 to 80:20, morepreferably 95:5 to 85:15.

Preference is given in accordance with one aspect of the invention to abarrier paper wherein the barrier paper additionally comprises aninterlayer 13 and the interlayer 13 is disposed between the papersubstrate and the barrier layer. In our own investigations it hasemerged that the properties of the resultant barrier paper areparticularly good if the barrier layer is not applied directly to thebase paper as paper substrate, but instead first an interlayer isapplied to the paper substrate.

It is preferred in accordance with one aspect of the invention here ifthe interlayer 13 comprises a pigment.

Preference is given in accordance with the invention to a barrier paperif the pigment is an organic pigment, inorganic pigment, or a mixture oforganic pigments and inorganic pigments.

Preference is given in accordance with one aspect of the invention to abarrier paper if the pigment is an inorganic pigment selected from thelist consisting of calcined kaolin, kaolin, kaolinite, hydratedmagnesium silicate, silicon oxide, bentonite, calcium carbonate,aluminum hydroxide, aluminum oxide, and boehmite.

Our own investigations have shown that particularly good properties canbe obtained if the pigment is lamellar in formation, preferably with anaspect ratio of 5 to 100, more preferably of 15 to 100, very preferablyof 20 to 80. The aspect ratio is the quotient formed between thediameter and the thickness of the lamellar pigment platelet prior tomixing with the further components. An aspect ratio of 20 means that thediameter of the platelet is 20 times greater than the thickness of theplatelet. Kaolin, kaolinite, and talc, for example, are lamellar andtherefore particularly preferred as pigment.

Preference is given in accordance with one aspect of the invention to abarrier paper if the mass fraction of the pigment in the interlayer is 5to 60%, preferably 15 to 40%, more preferably 20 to 40%, based on thetotal mass of the interlayer.

Preference is given in accordance with one aspect of the invention to abarrier paper if the interlayer comprises a binder and the binder ispreferably a crosslinked or noncrosslinked binder selected from thegroup consisting of starch, polyvinyl alcohol, carboxyl group-modifiedpolyvinyl alcohol, ethylene-vinyl alcohol copolymer, a combination ofpolyvinyl alcohol and ethylene-vinyl alcohol copolymer, ethylene-vinylacetate copolymer, silanol group-modified polyvinyl alcohol,diacetone-modified polyvinyl alcohol, acrylate copolymer, modifiedpolyethylene glycol, unmodified polyethylene glycol,α-isodecyl-ω-hydroxy-poly(oxy-1,2-ethanediyl), styrene-butadiene latex,styrene-acrylate polymers, film-forming acrylic copolymers, and mixturesthereof.

Preference is given in accordance with one aspect of the invention to abarrier paper if the binder comprises or consists of one or moreacrylate copolymers and/or styrene-acrylate polymers.

Preference is given in accordance with one aspect of the invention to abarrier paper if the mass fraction of the binder in the interlayer is 95to 40%, preferably 85 to 60%, more preferably 80 to 60%, based on thetotal mass of the interlayer.

Preferred in accordance with one aspect of the invention are barrierpapers wherein the mass per unit area of the interlayer is in the rangefrom 1.5 to 6 g/m², preferably in the range from 2.0 to 5.5 g/m², morepreferably in the range from 2.0 to 4.8 g/m².

Preferred in accordance with one aspect of the invention are barrierpapers wherein the paper substrate features a short-fiber pulp having aSchopper-Riegler freeness of at least 30° SR and a long-fiber pulphaving a Schopper-Riegler freeness of at least 25° SR and wherein thepaper substrate comprises at least a mass fraction of 50% of short-fiberpulp, based on the total mass of short-fiber pulp and long-fiber pulp.

It is further preferred if the short-fiber pulp has a Schopper-Rieglerfreeness of at least 35° SR, preferably of at least 39° SR, and/or thelong-fiber pulp has a Schopper-Riegler freeness of at least 30° SR,preferably of at least 33° SR.

It is preferred in accordance with one aspect of the invention if thepaper substrate comprises a mass fraction of at least 70% of short-fiberpulp, preferably between 70 and 75% of short-fiber pulp, based on thetotal mass of short-fiber pulp and long-fiber pulp.

It is preferred in accordance with one aspect of the invention if thebarrier paper on one side or on both sides has a Bekk smoothness,determined to ISO 5627, in the range from 100 to 1200 s. It is preferredhere if the barrier layer has a Bekk smoothness in the range from 100 to1200 s insofar as the barrier layer is an outer layer. In deviation fromISO 5627, the Bekk smoothness in this case is determined not on bothsides of the barrier paper, but only on the barrier layer of the barrierpaper.

Preference is given in accordance with one aspect of the invention to abarrier paper if the barrier paper has a water vapor permeability to DIN53122-1 of less than or equal to 300 g/(m²d), preferably less than orequal to 250 g/(m²d), more preferably of less than or equal to 150g/(m²d).

Surprisingly it has emerged that the barrier paper of one aspect of theinvention has not only a very high resistance toward fat but also a lowwater vapor permeability. A low water vapor permeability in the case ofpackaging is desirable in the case of foods because the packaged foodsdo not dry out prematurely and remain fresh for longer.

Preference is given in accordance with one aspect of the invention to abarrier paper if the barrier paper has a KIT rating of at least 5,preferably of at least 8, more preferably of at least 12, measuredaccording to the Tappi 559 method.

Our own investigations have shown that barrier papers of one aspect ofthe invention can have a KIT rating of more than 12 and hence exhibitexcellent bed resistance, situated within the same range as the fatresistance of barrier papers coated with polymeric or aluminum foil.

Preference is given in accordance with one aspect of the invention to abarrier paper if the barrier paper has a fat permeability withturpentine oil to Tappi 454 of at least 1300 s, preferably of at least1500 s, more preferably of at least 1800 s.

Preference is given in accordance with one aspect of the invention to abarrier paper wherein the barrier paper has a fat permeability of atleast level 5, preferably of at least level 3, more preferably of atleast level 1, measured by the DIN 53116 method.

Preference is given in accordance with one aspect of the invention to abarrier paper if the mass per unit area of the barrier paper is in therange from 30 to 120 g/m², preferably in the range from 35 to 80 g/m²,more preferably in the range from 40 to 50 g/m².

In certain embodiments of the paper of one aspect of the invention it isadvantageous if the carrier paper used is paper, paperboard orcardboard. Especially where paperboard or cardboard is used as carrierpaper, the mass per unit area of the resultant barrier paper is higherthan 120 g/m². Preferably the mass per unit area is in the range from120 g/m² to 600 g/m² in the case of cardboard and more than 600 g/m² inthe case of cardboard.

Preference is given in accordance with one aspect of the invention to abarrier paper if the wax based on a vegetable oil and the polymericbinder are distributed homogeneously in the barrier layer. In this caseit is not absolutely necessary for the wax and the polymeric binder tobe thoroughly mixed; instead, there may be local differences inconcentration, resulting from the specific production using small waxparticles. In accordance with the invention, however, the wax is notencapsulated—in other words, it does not have a core-shell structure.

Preferred in accordance with one aspect of the invention is a barrierpaper for use as wrapping paper, lining paper, interleaving paper and/orrelease paper for foods, preferably for the packaging of bakeryproducts, sandwiches, bread, burgers, meat products, fish, sausageproducts and/or cheese.

In one embodiment of the barrier paper of one aspect of the invention,the paper substrate is coated both to the front side and to the backside with the barrier layer, and preferably there is an interlayerdisposed in each case between the barrier layers and the papersubstrate. Regarding the embodiment of the interlayers, reference ismade to the observations above concerning the interlayer.

Especially in the embodiment with two barrier layers, but also in theembodiment with only one barrier layer, it has emerged, surprisingly,that the barrier papers of the invention not only have excellentresistance toward fats and/or oils and/or moisture, but also, moreover,possess a barrier effect or blocking effect with respect to mineraloils. Mineral oils occur frequently in recycled papers or paperboardsthat are not intended for the direct packaging of foods. Where, however,they do come into contact with foods, as for example if foods aredispatched in a cardboard box, it is impossible to rule out mineral oilstransferring onto the food, even if the foods are packed in a separatepackaging. In the past, for example, mineral oil residues have beenfound in chocolate from Advent calenders, having been absorbed from thechocolate by the contact of the chocolate with the cardboard packaging.Barrier papers of the invention are notable, surprisingly, for not onlypreventing the emergence of fats, oils, and moisture from the food tothe outside, but also, additionally, protecting the food packagedtherewith from contamination by mineral oils.

It is also possible, for example, to produce packaging cartons frombarrier papers of the invention, these cartons having the barrier layerin the interior of the packaging carton. Alternatively it is alsopossible to produce inner-bag packaging from barrier papers of oneaspect of the invention.

A further aspect of the present invention relates to the use of abarrier paper of the invention as wrapping paper, lining paper, paperfor inner-bag packaging, interleaving paper and/or release paper forfoods, preferably for the wrapping, lining, interleaving and/orseparation of bakery products, fried and/or deep-fried products, snackproducts, sandwiches, bread, burgers, meat products, fish products,sausage products, and/or cheese.

A further aspect of the present invention relates to the use of abarrier paper of the invention for packaging foods, preferably forpackaging fatty foods, with the barrier paper repelling the fat from thefood.

A further aspect of the present invention relates to a method forproducing a barrier paper, preferably a barrier paper of the invention,comprising the following steps:

-   -   (i) producing or providing a paper substrate,    -   (ii) producing or providing a barrier coat comprising a wax        emulsion, the wax being a wax based on a vegetable oil,    -   (iii) applying the produced or provided barrier coat to one        sides of the paper substrate and subsequently drying the barrier        coat, to give a barrier layer.

In this case it is preferred in accordance with one aspect of theinvention if the wax emulsion is a wax-in-oil emulsion and the waxemulsion additionally comprises an anionic polymeric binder which ispreferably suitable for stabilizing the wax emulsion.

It is preferred in accordance with one aspect of the invention in thiscase if the produced or provided barrier coat comprises a (further)polymeric binder besides the wax emulsion.

It is preferred in accordance with one aspect of the invention if theaverage particle size of the wax particles is in the range from 600 to1100 nm, preferably in the range from 700 to 1000 nm. The particle sizeof the wax particles can be determined using laser diffraction particlesize analysis. Our own investigations have shown that particles of thisorder of size lead to barrier layers having very good barrier andmechanical properties, since there is effective mixing between polymericbinder and wax particles.

It is preferred in accordance with one aspect of the invention if thewax emulsion is basic and preferably has a pH in the range from 8 to 10.

It is preferred in accordance with one aspect of the invention if thewax based on a vegetable oil is a soy wax.

It is preferred in accordance with one aspect of the invention if thedrying of the barrier coat takes place at a temperature above themelting point of the wax (e.g., at 40, 60, 80 or 100° C.) and/or in aseparate step the paper substrate comprising the (optionally dried)barrier coat is heated above the melting point of the wax (e.g., at 40,60, 80 or 100° C.).

In an embodiment of the method that is in accordance with one aspect ofthe invention, a coated paper substrate is used as paper substrate or acoat is applied to one sides of the paper substrate and the coat is thendried, to give an interlayer, before the barrier coat is applied.Preferably, therefore, the method of one aspect of the inventionadditionally comprises the following steps:

a) producing or providing a coat comprising pigments and binders,

b) applying the produced or provided coat to one side of the papersubstrate and subsequently drying the coat, to give an interlayer, wherethe steps a) and b) are carried out preferably between the steps i) andii).

A further aspect of one aspect of the present invention relates to abarrier paper produced by a method of the invention.

A further aspect of the present invention relates to a the use of a waxbased on a vegetable oil for producing a paper coating, preferably forproducing a barrier layer of a barrier paper.

In the context of one aspect of the present invention, preferably two ormore of the aspects identified above as being preferred are realized atthe same time; especially preferred are those combinations of suchaspects, and of the corresponding features, that arise from the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments are apparent from the examples and working examplesthat are elucidated in more detail by means of the figures. In thesefigures:

FIG. 1 is a layer construction of barrier paper;

FIG. 2 is a layer construction of barrier paper;

FIG. 3 is a layer construction of barrier paper; and

FIG. 4 is a layer construction of barrier paper.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1 shows a barrier paper 10 that consists of a paper substrate 11and a barrier layer 12. The paper substrate has a front side and a backside opposite the front side, and disposed on the front side of thepaper substrate 11 is a barrier layer 12, which consists of a polymericbinder and a wax based on a vegetable oil.

FIG. 2 shows a barrier paper 10 that consists of a paper substrate 11,an interlayer 13, and a barrier layer 12. The paper substrate has afront side and a back side opposite the front side, and disposed on thefront side of the paper substrate 11 is the interlayer 13. Disposed onthe interlayer 13 in turn is the barrier layer 12, which consists of apolymeric binder and a wax based on a vegetable oil. The interlayer 13preferably comprises a pigment and a binder.

FIG. 3 shows a barrier paper 10 that consists of a paper substrate 11and two barrier layers 12. The paper substrate has a front side and aback side opposite the front side, and disposed on each of the frontside and the back side of the paper substrate 11 is a respective barrierlayer 12, which consists of a polymeric binder and a wax based on avegetable oil.

FIG. 4 shows a barrier paper 10 that consists of a paper substrate 11,two interlayers 13, and two barrier layers 12. The paper substrate has afront side and a back side opposite the front side, and, disposed oneach of the front side and the back side of the paper substrate 11,there is a respective interlayer 13. Disposed on each of the interlayers13 in turn is a respective barrier layer 12, which consists of apolymeric binder and a wax based on a vegetable oil. The interlayerspreferably comprise a pigment and a binder.

Example 1: Production of a Barrier Paper of the Invention

As paper substrate, a paper web provided with resin sizing in the stockand having a mass per unit area of 33.3 g/m² was produced on a papermachine from short-fiber stocks (100% short-fiber pulp) having afreeness of 50° SR and with addition of talc as filler with a massfraction of 1%, based on the total mass of the paper substrate. Thepaper substrate produced was calendered under a linear load of 100 kN/mand a temperature of 100° C.

A curtain coater was used to apply, to the front side, a priming coatcomprising water, an aqueous dispersion of an acrylic-acetate copolymer(solids content 33%, mass fraction in the priming coat 0.03% (oven-dry);Sterocoll BL), an aqueous dispersion of an acrylic copolymer (solidscontent 40%, mass fraction in the priming coat 1.27% (oven-dry); tradename: Sterocoll FS), an aqueous dispersion of a styrene-acrylatecopolymer (solids content 50%, mass fraction in the priming coat 70.5%(oven-dry); trade name: Sterocoll FS), and kaolin (solids content 70%,mass fraction in the priming coat 28.2% (oven-dry); trade name: CapimNP), with a coat weight of 3.5 g/m², and the priming coat wassubsequently dried by IR and air drying, to give an interlayer.

A curtain coater was used to apply, to the interlayer, a barrier coatcomprising water, a wax based on a vegetable oil (solids content 30%,mass fraction in the priming coat 82% (oven-dry); trade name: SWX 155),a polyacrylate dispersion (solids content 48%, mass fraction in thepriming coat 16.4% (oven-dry); trade name: Tecryl PB 16/3), and amixture of nonionic surfactants (solids content 100%, mass fraction inthe priming coat 1.6% (oven-dry); trade name: Metolat 700), with a coatweight of 4 g/m², and the barrier coat was subsequently dried by meansof IR and air drying, to give a barrier layer.

Samples were taken from the completed barrier paper, and typicalparameters were determined from these samples and are collated in thetable below.

KIT rating (Tappi 559) >12 Water vapor permeability 23° C./85% rh 115g/(m²d) Water vapor permeability 38° C./90% rh 249 g/(m²d) Fatresistance palm kernel fat method I 8 breakthroughs (<1 mm) setting I >24 h with weight 0 breakthroughs (>1 mm) Fat resistance palm kernel fatmethod II 0 breakthroughs (<1 mm) setting I > 24 h with weight 4breakthroughs (>1 mm)

The results show that the barrier paper of the invention exhibits fatresistance outstandingly and a low water vapor permeability.

Thus, while there have shown and described and pointed out fundamentalnovel features of the invention as applied to a preferred embodimentthereof, it will be understood that various omissions and substitutionsand changes in the form and details of the devices illustrated, and intheir operation, may be made by those skilled in the art withoutdeparting from the spirit of the invention. For example, it is expresslyintended that all combinations of those elements and/or method stepswhich perform substantially the same function in substantially the sameway to achieve the same results are within the scope of the invention.Moreover, it should be recognized that structures and/or elements and/ormethod steps shown and/or described in connection with any disclosedform or embodiment of the invention may be incorporated in any otherdisclosed or described or suggested form or embodiment as a generalmatter of design choice. It is the intention, therefore, to be limitedonly as indicated by the scope of the claims appended hereto.

1.-16. (canceled)
 17. A barrier paper comprising: a paper substratehaving a front side and a back side opposite the front side; and abarrier layer disposed on the front side and/or back side of the papersubstrate, wherein the barrier layer comprises at least a polymericbinder and a wax based on a vegetable oil.
 18. The barrier paper asclaimed in claim 17, wherein the wax based on a vegetable oil is a waxbased on an oil selected from one or more of palm oil, coconut oil,poppyseed oil, olive oil, linseed oil, soybean oil, sunflower oil,safflower oil, and rapeseed oil.
 19. The barrier paper as claimed inclaim 17, wherein the wax based on a vegetable oil is a wax based on asoybean oil.
 20. The barrier paper as claimed in claim 17, wherein amass fraction of the wax in the barrier layer is at least one of: 6 to98% based on a total mass of the barrier layer, 20 to 90% based on thetotal mass of the barrier layer, and 50 to 89%, based on the total massof the barrier layer.
 21. The barrier paper as claimed in claim 17,wherein a mass fraction of the wax in the barrier layer is 20 to 78%.22. The barrier paper as claimed in claim 17, wherein the wax has amelting point of above at least one of 40° C., 50° C., and 60° C. 23.The barrier paper as claimed in claim 17, wherein the polymeric binderis a crosslinked or noncrosslinked binder selected from the groupconsisting of starch, polyvinyl alcohol, carboxyl group-modifiedpolyvinyl alcohol, ethylene-vinyl alcohol copolymer, a combination ofpolyvinyl alcohol and ethylene-vinyl alcohol copolymer, ethylene-vinylacetate copolymer, silanol group-modified polyvinyl alcohol,diacetone-modified polyvinyl alcohol, acrylate copolymer, modifiedpolyethylene glycol, unmodified polyethylene glycol,α-isodecyl-ω-hydroxy-poly(oxy-1,2-ethanediyl), styrene-butadiene latex,styrene-acrylate polymers, and mixtures thereof.
 24. The barrier paperas claimed in claim 17, wherein the polymeric binder comprises one ormore styrene-acrylate polymers.
 25. The barrier paper as claimed inclaim 24, wherein the acrylate copolymer is a copolymer prepared usingtwo or more monomers selected from the group consisting of methylacrylate, methyl methacrylate, butyl acrylate, butyl methacrylate,2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, and styrene.
 26. Thebarrier paper as claimed in claim 17, wherein a mass fraction of thepolymeric binder in the barrier layer is at least one of: 94 to 2% basedon a total mass of the barrier layer, 80 to 10% based on the total massof the barrier layer, and 50 to 11% based on the total mass of thebarrier layer.
 27. The barrier paper as claimed in claim 17, wherein thebarrier layer further comprises a wax based on saturated hydrocarbons.28. The barrier paper as claimed in claim 27, wherein the wax based onsaturated hydrocarbons has a melting point of above at least one of 40°C., 50° C., and 60° C.
 29. The barrier paper as claimed in claim 27,wherein the wax based on saturated hydrocarbons comprises at least onealkane selected from the group consisting of heneicosane, docosane,tricosane, tetracosane, pentacosane, hexacosane, heptacosane,octacosane, nonacosane, triacontane, hentriacontane, dotriacontane,tritriacontane, tetratriacontane, pentatriacontane, hexatriacontane,heptatriacontane, octatriacontane, and nonatriacontane.
 30. The barrierpaper as claimed in claim 17, further comprising: an interlayer disposedbetween the paper substrate and the barrier layer.
 31. The barrier paperas claimed in claim 17, wherein the barrier paper is configured as oneor more of wrapping paper, lining paper, interleaving paper and/orrelease paper for foods, for wrapping, lining, interleaving and/orseparating of bakery products, fried and/or deep-fried products, snackproducts, sandwiches, bread, burgers, meat products, fish products,sausage products, and/or cheese.
 32. A method for producing a barrierpaper, comprising: (i) one of producing and providing a paper substrate;(ii) one of producing and providing a barrier coat comprising a waxemulsion, wherein the wax is based on a vegetable oil; and (iii)applying the barrier coat to one side of the paper substrate andsubsequently drying the barrier coat, to provide a barrier layer. 33.The method for producing a barrier paper of claim 32, furthercomprising: (iv) disposing an interlayer between the paper substrate andthe barrier layer.